Method for carbonylation of lower aliphatic alcohols using tin promoted platinum catalyst

ABSTRACT

A vapor-phase carbonylation method for producing esters and carboxylic acids from reactants comprising lower alkyl alcohols, lower alkyl alcohol generating compositions and mixtures thereof. The method includes contacting the reactants and carbon monoxide in a carbonylation zone of a carbonylation reactor under vapor-phase conditions with a catalyst having a catalytically effective amount of platinum and tin associated with a solid carrier material.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to a method for the vapor-phasecarbonylation of lower alkyl alcohols, ether and ester derivatives ofthe alcohols, and mixtures thereof to produce esters and carboxylicacids. Particularly, the present invention relates to a method for thevapor-phase carbonylation of methanol to produce acetic acid and methylacetate using a solid catalyst having platinum and tin associated with asolid support material.

[0002] Lower carboxylic acids and esters such as acetic acid and methylacetate have been known as industrial chemicals for many years. Aceticacid is used in the manufacture of a variety of intermediary andend-products. For example, an important derivative is vinyl acetate thatcan be used as a monomer or co-monomer for a variety of polymers. Aceticacid itself is used as a solvent in the production of terephthalic acid,which is widely used in the container industry, and particularly in theformation of PET beverage containers.

[0003] There has been considerable research activity in the use of metalcatalysts for the carbonylation of lower alkyl alcohols, such asmethanol, and ethers to their corresponding carboxylic acids and esters,as illustrated in equations 1-3 below:

ROH+CO→RCOOH  (1)

2ROH+CO→RCOOR+water  (2)

ROR+CO→RCOOR  (3)

[0004] Carbonylation of methanol is a well-known reaction and istypically carried out in the liquid phase with a catalyst. A thoroughreview of these commercial processes and other approaches toaccomplishing the formation of acetyl from a single carbon source isdescribed by Howard et al. in Catalysis Today, 18, 325-354 (1993).Generally, the liquid phase carbonylation reactions for the preparationof acetic acid using methanol are performed using homogeneous catalystsystems comprising a Group VIII metal and a halogen component such asiodine or bromine or an iodine or bromine-containing compound such ashydrogen iodide, hydrogen bromide, methyl iodide, or methyl bromide.Rhodium is the most common Group VIII metal catalyst and methyl iodideis the most common promoter. These reactions are conducted in thepresence of water to prevent precipitation of the catalyst.

[0005] These recently developed processes represent a distinctimprovement over the classic carbonylation processes wherein such feedmaterials have been previously carbonylated in the presence of suchcatalyst systems as phosphoric acid, phosphates, activated carbon, heavymetal salts and metal carbonyls such as cobalt carbonyl, iron carbonyland nickel carbonyl. All of these previously known processes require theuse of extremely high partial pressures of carbon monoxide. They alsohave the disadvantage of requiring higher catalyst concentrations,longer reaction times, and higher temperatures to obtain substantialreaction and conversion rates. This results in needing larger and morecostly processing equipment and higher manufacturing costs.

[0006] A disadvantage of a homogeneous phase carbonylation process isthat additional steps are necessary for separating the products from thecatalyst solutions, and there are always handling losses of thecatalyst. Losses of the metal in the catalyst can be attributed toseveral factors, such as the plating-out of the active metal onto pipingand process equipment thereby rendering the metal inactive forcarbonylation purposes and losses due to incomplete separation of thecatalyst from the products. These losses of the metal component arecostly because the metals themselves are very expensive.

[0007] Schultz, in U.S. Pat. No. 3,689,533, discloses using a supportedrhodium heterogeneous catalyst for the carbonylation of alcohols to formcarboxylic acids in a vapor-phase reaction. Schultz further disclosesthe presence of a halide promoter.

[0008] Schultz in U.S. Pat. No. 3,717,670 describes a similar supportedrhodium catalyst in combination with promoters selected from Groups IB,IIIB, IVB, VB, VIB, VIII, lanthanide and actinide elements of thePeriodic Table.

[0009] Uhm, in U.S. Pat. No. 5,488,143, describes the use of alkali,alkaline earth or transition metals as promoters for supported rhodiumfor the halide-promoted, vapor phase methanol carbonylation reaction.Pimblett, in U.S. Pat. No. 5,258,549, teaches that the combination ofrhodium and nickel on a carbon support is more active than either metalby itself.

[0010] In addition to the use of iridium as a homogeneous alcoholcarbonylation catalyst, Paulik et al., in U.S. Pat. No. 3,772,380,describe the use of iridium on an inert support as a catalyst in thevapor phase, halogen-promoted, heterogeneous alcohol carbonylationprocess.

[0011] European Patent Application EP 0 759 419 A1 pertains to a processfor the carbonylation of an alcohol and/or a reactive derivativethereof. EP 0 759 419 A1 discloses a carbonylation process comprising afirst carbonylation reactor wherein an alcohol is carbonylated in theliquid phase in the presence of a homogeneous catalyst system and theoff gas from this first reactor is then mixed with additional alcoholand fed to a second reactor containing a supported catalyst. Thehomogeneous catalyst system utilized in the first reactor comprises ahalogen component and a Group VIII metal selected from rhodium andiridium. When the Group VIII metal is iridium, the homogeneous catalystsystem also may contain an optional co-promoter selected from the groupconsisting of ruthenium, osmium, rhenium, cadmium, mercury, zinc, indiumand gallium. The supported catalyst employed in the second reactorcomprises a Group VIII metal selected from the group consisting ofiridium, rhodium, and nickel, and an optional metal promoter on a carbonsupport. The optional metal promoter may be iron, nickel, lithium andcobalt. The conditions within the second carbonylation reactor zone aresuch that mixed vapor and liquid phases are present in the secondreactor. The presence of a liquid phase component in the second reactorinevitably leads to leaching of the active metals from the supportedcatalyst which, in turn, results in a substantial decrease in theactivity of the catalyst and costly replacement of the active catalystcomponent.

[0012] The literature contains several reports of the use ofrhodium-containing zeolites as vapor phase alcohol carbonylationcatalysts at one bar pressure in the presence of halide promoters. Thelead references on this type of catalyst are presented by Maneck et al.in Catalysis Today, 3, 421-429 (1988). Gelin et al., in Pure & Appl.Chem., Vol. 60, No. 8, 1315-1320 (1988), provide examples of the use ofrhodium or iridium contained in zeolite as catalysts for the vapor phasecarbonylation of methanol in the presence of halide promoter. Krzywickiet al., in Journal of Molecular Catalysis, 6, 431-440 (1979), describethe use of silica, alumina, silica-alumina and titanium dioxide assupports for rhodium in the halide-promoted vapor phase carbonylation ofmethanol, but these supports are generally not as efficient as carbon.Luft et al., in U.S. Pat. No. 4,776,987 and in related disclosures,describe the use of chelating ligands chemically attached to varioussupports as a means to attach Group VIII metals to a heterogeneouscatalyst for the halide-promoted vapor phase carbonylation of ethers oresters to carboxylic anhydrides.

[0013] Evans et al., in U.S. Pat. No. 5,185,462, describe heterogeneouscatalysts for halide-promoted vapor phase methanol carbonylation basedon noble metals attached to nitrogen or phosphorus ligands attached toan oxide support.

[0014] Panster et al., in U.S. Pat. No. 4,845,163, describe the use ofrhodium-containing organopolysiloxane-ammonium compounds asheterogeneous catalysts for the halide-promoted liquid phasecarbonylation of alcohols.

[0015] Drago et al., in U.S. Pat. No. 4,417,077, describe the use ofanion exchange resins bonded to anionic forms of a single transitionmetal as catalysts for a number of carbonylation reactions including thehalide-promoted carbonylation of methanol. Although supported ligandsand anion exchange resins may be of some use for immobilizing metals inliquid phase carbonylation reactions, in general, the use of supportedligands and anion exchange resins offer no advantage in the vapor phasecarbonylation of alcohols compared to the use of the carbon as a supportfor the active metal component. Typically, these catalysts are unstableat elevated temperatures making them poorly suited to vapor phaseprocesses.

[0016] Nickel on activated carbon has been studied as a heterogeneouscatalyst for the halide-promoted vapor phase carbonylation of methanol.Relevant references to the nickel-on-carbon catalyst systems areprovided by Fujimoto et al. in Chemistry Letters 895-898, (1987).Moreover, Fujimoto et al. in Journal of Catalysis, 133, 370-382 (1992)observed increased rates when hydrogen is added to the feed mixture. Liuet al., in Ind. Eng. Chem. Res., 33 488-492, (1994), report that tinenhances the activity of the nickel-on-carbon catalyst. Mueller et al.,in U.S. Pat. No. 4,918,218, disclose the addition of palladium andoptionally copper to supported nickel catalysts for the halide-promotedcarbonylation of methanol. In general the rates of reaction provided bynickel-based catalysts are lower than those provided by the analogousrhodium-based catalysts when operated under similar conditions.

[0017] Other single metals supported on carbon have been reported byFujimoto et al. in Catalysis Letters, 2, 145-148 (1989) to have limitedactivity in the halide-promoted vapor phase carbonylation of methanol.The most active of these metals is Sn. Following Sn in order ofdecreasing activity are Pb, Mn, Mo, Cu, Cd, Cr, Re, V, Se, W, Ge and Ga.None of these other single metal catalysts are nearly as active as thosebased on Rh, Ir, Ni or the catalyst of the present invention.

[0018] Yagita and Fujimoto in Journal of Molecular Catalysis, 69,191-197 (1991) examined the role of activated carbon in a metalsupported catalyst and observed that the carbonylation activities ofGroup VIII metals supported on activated carbon are ordered by theaffinities between the metal and the halogen.

[0019] Feitler, in U.S. Pat. No. 4,612,387, describes the use of certainzeolites containing no transition metals as catalysts for thehalide-free carbonylation of alcohols and other compounds in the vaporphase.

[0020] U.S. Pat. No. 5,218,140, describes a vapor phase process forconverting alcohols and ethers to carboxylic acids and esters by thecarbonylation of alcohols and ethers with carbon monoxide in thepresence of a metal ion exchanged heteropoly acid supported on an inertsupport. The catalyst used in the reaction includes a polyoxometallateanion in which the metal is at least one of a Group V(a) and VI(a) iscomplexed with at least one Group VIII cation such as Fe, Ru, Os, Co,Rh, Ir, Ni, Pd or Pt as catalysts for the halide-free carbonylation ofalcohols and other compounds in the vapor phase.

[0021] In accordance with the present invention, a method for theheterogeneous vapor-phase carbonylation of reactants comprising loweralkyl alcohols, ether and ester derivatives of the alcohols, andester-alcohols mixtures is provided using a catalyst that includes acatalytically effective amount of platinum and tin associated with asolid support material which, desirably, is inert to the carbonylationreaction.

SUMMARY OF THE INVENTION

[0022] Briefly, the present invention is a method for the vapor-phasecarbonylation of reactants comprising lower alkyl alcohols, lower alkylalcohol generating compositions such as ether and ester derivatives ofthe alcohols, and mixtures thereof for producing esters and carboxylicacids. The method includes contacting the reactants under vapor-phasecarbonylation reaction conditions with a heterogeneous catalyst having acatalytically effective amount of platinum and/or platinum salt and tinand/or tin salt associated with a solid support material. In a preferredembodiment, the method also includes contacting the reactants, in thepresence of the solid catalyst, with a vaporous halide promoter. As usedherein the term “associated with” means any manner for incorporating orassociating the platinum metal and/or its salt and the tin metal and/orits salt on or in the solid support material. Non-limiting examples inwhich the platinum and tin metals or their respective salts may beassociated with the solid support include impregnating, immersing,spraying and coating the support with a solution containing platinum andwith a solution containing tin sequentially or impregnating, immersing,spraying and coating the support with a solution containing a mixture ofplatinum and tin.

[0023] It is an object of the invention to provide a method for thecarbonylation of lower alkyl alcohols, ethers, and ester-alcoholmixtures to produce esters and carboxylic acids. More particularly, itis an object of the present invention to provide a vapor-phasecarbonylation method for the production of acetic acid, methyl acetateand mixtures thereof from a lower alkyl alcohol and preferably,methanol.

[0024] It is another object of the invention to provide a process inwhich the catalyst is maintained in a solid phase to reduce or eliminatethe handling losses of the catalyst.

[0025] It is another object of the invention to provide a vapor phasecarbonylation process for the production of acetic acid and methylacetate which utilizes a more stable catalyst and reduces the need forcatalyst recovery and recycle as well as solvent recovery.

[0026] These and other objects and advantages of the invention willbecome apparent to those skilled in the art from the accompanyingdetailed description.

DETAILED DESCRIPTION OF THE INVENTION

[0027] In accordance with the invention, a vapor-phase carbonylationmethod is provided for the continuous production of carboxylic acids andesters by contacting lower alkyl alcohols, lower alkyl alcoholgenerating compositions such as ether and/or ester derivatives of thealcohol, and mixtures thereof, and carbon monoxide with a solidsupported catalyst. The catalyst includes an effective amount ofplatinum and/or platinum salt and tin and/or tin salt associated with asolid support material which, desirably, is inert to the carbonylationreaction. In a preferred embodiment of the present process, the reactantis fed in conjunction with a vaporous halide promoter. In a preferredembodiment, the present invention provides for the vapor-phasecarbonylation of methanol for the continuous production of acetic acid,methyl acetate or mixtures thereof.

[0028] The process of this invention is operated in the vapor phase and,therefore, is practiced at temperatures above the dew point of thereactants and product mixture, i.e., the temperature at whichcondensation occurs. However, since the dew point is a complex functionof dilution (particularly with respect to non-condensable gases such asunreacted carbon monoxide, hydrogen, or inert diluent gas), reactant andproduct composition, and pressure, the process may still be operatedover a wide range of temperatures, provided the temperature exceeds thedew point of the reactants and products. In practice, this generallydictates a temperature range of about 100° C. to 500° C., withtemperatures in the range of 100° C. to 325° C. being preferred andtemperature of about 150° C. to 275° C. being particularly useful.Advantageously, operating in the vapor phase eliminates catalystdissolution, i.e., metal leaching from the catalyst support, whichoccurs in the known heterogeneous processes operating in the presence ofliquid compounds.

[0029] As with temperature, the useful pressure range for the vaporphase carbonylation is limited by the dew point of the product mixture.Provided that the reaction is operated at a temperature sufficient toprevent liquefaction of the reactants and products, a wide range ofpressures may be used, e.g., pressures in the range of about 0.1 to 100bars absolute. The process preferably is carried out at a pressure inthe range of about 1 to 50 bars absolute, most preferably, about 3 to 30bar absolute (bara).

[0030] Suitable feedstock, i.e., reactants, for carbonylation using thecatalyst of the present invention include lower alkyl alcohols, loweralkyl alcohol generating compositions such as ether and esterderivatives of the alcohols, and mixtures thereof. Non-limiting examplesof reactants include alcohols and ethers in which an aliphatic carbonatom is directly bonded to an oxygen atom of either an alcoholichydroxyl group in the compound or an ether oxygen in the compound andmay further include aromatic moieties. Preferably, the feedstock is oneor more lower alkyl alcohols having from 1 to 10 carbon atoms andpreferably having from 1 to 6 carbon atoms, alkane polyols having 2 to 6carbon atoms, alkyl alkylene polyethers having 3 to 20 carbon atoms andalkoxyalkanols having from 3 to 10 carbon atoms. The most preferredreactant is methanol. Although methanol is preferably used in theprocess and is normally fed as methanol, it can be supplied in the formof a combination of materials which generate methanol. Examples of suchcombination of materials include (i) methyl acetate and water and (ii)dimethyl ether and water. In the operation of the process, both methylacetate and dimethyl ether are formed within the reactor and, unlessmethyl acetate is the desired product, they are recycled with water tothe reactor where they are later consumed to form acetic acid.

[0031] Although the presence of water in the gaseous feed mixture is notessential when using methanol, the presence of some water is desirableto suppress formation of methyl acetate and/or dimethyl ether. Whenusing methanol to generate acetic acid, the molar ratio of water tomethanol can be 0:1 to 10:1, but preferably is in the range of 0.01:1 to1:1. When using an alternative source of methanol such as methyl acetateor dimethyl ether, the amount of water fed usually is increased toaccount for the mole of water required for hydrolysis of the methanolalternative. Accordingly, when using either methyl acetate or dimethylether, the mole ratio of water to ester or ether is in the range of 1:1to 10:1, but preferably in the range of 1:1 to 3:1. In the preparationof acetic acid, it is apparent that combinations of methanol, methylester, and/or dimethyl ether are equivalent, provided the appropriateamount of water is added to hydrolyze the ether or ester to provide themethanol reactant.

[0032] When the methyl ester, methyl acetate, is the desired product, nowater should be added to the carbonylation process and dimethyl etherbecomes the preferred feedstock. Further, when methanol is used as thefeedstock in the preparation of methyl acetate, it is necessary toremove water. However, the primary utility of the process of the presentinvention is in the manufacture of acetic acid.

[0033] In the practice of a vapor-phase carbonylation process, thereactant, in the vapor phase, is passed through or over the solidsupported platinum and tin catalyst and preferably the reactant is fedin conjunction with a vaporous halide promoter.

[0034] In preparing the solid supported catalyst, the form of platinumused generally is not critical. The solid supported component of thecatalyst may be prepared from a wide variety of platinum containingcompounds. For example, the platinum compound can be in the form of asalt of a mineral acid halide, such as chloroplatinic acid; trivalentnitrogen compounds such as dichlorodiammine platinum; organic compoundsof trivalent phosphorous, such as dichlorobis(triphenylphosphine)platinum; olefins, such as dichloro(1,5-cyclooctadiene) platinum;nitrites, such as dichlorobis(benzonitrile) platinum and oxides ofplatinum may be used if dissolved in the appropriate medium either aloneor in combination. The preferred sources of platinum is one of itchlorides, such as any of the various salts of hexachloroplatinate(IV)or a solution of platinum dichloride in either aqueous HCl or aqueousammonia.

[0035] The amount of platinum, as metal, on the support can vary fromabout 0.01 weight percent to about 10 weight percent, with from about0.1 weight percent to about 2 weight percent platinum being preferred,wherein the weight percent is based on the total weight of the solidcatalyst.

[0036] Likewise, the form of tin used in preparing the solid supportedcatalyst is not critical and may include a wide variety of tincontaining compounds. For example, suitable tin compounds which may beassociated with the solid support material include tin halides such astin (II) chloride; alkyl carboxylate salts and aryl carboxylate saltswherein the alkyl group has from 1 to 10 carbon atoms and the aryl grouphas from 6 to 24 carbon atoms wherein at least one of the carbon atomsis bound to the tin moiety, tin oxides such as tin (II) oxalate, andmixtures of such tin containing compounds. The preferred sources of tinare tin (II) chloride, preferably dissolved in aqueous HCl, and tin (II)oxalate due to their availability, cost, lower toxicity, and highsolubility in water (the preferred solvent medium).

[0037] The content of tin, as metal, on the support can vary over a widerange, for example from about 0.01 to 10 weight percent tin based on thetotal weight of the solid supported catalyst. However, the preferredamount of tin in the catalyst is from about 0.1 to 5 weight percent oftin based on the total weight of the solid supported catalyst.

[0038] The solid support useful for acting as a carrier for the platinumand tin consists of a porous solid of such size that it can be employedin fixed or fluidized bed reactors. Typical support materials have asize of from about 400 mesh per inch to about ½ inch. Preferably, thesupport is carbon, including activated carbon, having a high surfacearea. Activated carbon is well known in the art and may be derived fromcoal or peat having a density of from about 0.03 grams/cubic centimeter(g/cm³) to about 2.25 g/cm³. The carbon can have a surface area of fromabout 200 square meters/gram (m²/g) to about 1200 m²/g. Other solidsupport materials which may be used in accordance with the presentinvention include pumice, alumina, silica, silica-alumina, magnesia,diatomaceous earth, bauxite, titania, zirconia, clays, magnesiumsilicate, silicon carbide, zeolites, and ceramics. The shape of thesolid support is not particularly important and can be regular orirregular and include extrudates, rods, balls, broken pieces and thelike disposed within the reactor.

[0039] The platinum and tin can be associated with the solid support bysolubilizing the metals, or their respective salts, in a suitablesolvent and contacting the solubilized platinum and tin with the solidsupport material. The solvent is then evaporated so that at least aportion of the platinum and tin is associated with the solid support.Drying temperatures can range from about 100° C. to about 600° C. for aperiod greater than about one second. One skilled in the art willunderstand that the drying time is dependent upon the temperature,humidity, and solvent. Generally, lower temperatures require longerheating periods to effectively evaporate the solvent from the solidsupport. The method of preparing the solid component of the catalystoptionally further includes the step of heating the solid supportedplatinum and tin in a stream of inert gas. Non-limiting examples ofsuitable inert gases include nitrogen, argon and helium

[0040] Alternatively the platinum and tin can be associated with thesolid support by sequentially associating each metal with a supportmaterial. For example, platinum or a platinum containing salt would besolubilized using a suitable solvent. The dissolved metal solution wouldthen be contacted with the support material. Afterwards, the solvent isevaporated so that at least a portion of the platinum is associated withthe solid support material. Next, tin or a tin containing salt would beassociated with the support material following a similar procedure asdescribed for associating the platinum with the solid carrier. Thus, onewill understand that multiple layers of the respective platinum and tinmetals or metal containing compounds can be associated with the supportby merely following multiple steps of the procedure described above.

[0041] In a preferred embodiment, the method further includes contactingthe reactants, in the presence of the solid catalyst, with a vaporoushalide promoter selected from chlorine, bromine and iodine compounds.Preferably, the vaporous halide is selected from bromine and iodinecompounds that are vaporous under vapor-phase carbonylation conditionsof temperature and pressure. Suitable halides include hydrogen halidessuch as hydrogen iodide and gaseous hydriodic acid; alkyl and arylhalides having up to 12 carbon atoms such as, methyl iodide, ethyliodide, 1-iodopropane, 2-iodobutane, 1-iodobutane, methyl bromide, ethylbromide, benzyl iodide and mixtures thereof. Desirably, the halide is ahydrogen halide or an alkyl halide having up to 6 carbon atoms.Non-limiting examples of preferred halides include hydrogen iodide,methyl iodide, hydrogen bromide, methyl bromide and mixtures thereof Thehalide may also be a molecular halide such as I₂, Br₂, or Cl₂.

[0042] The molar ratio of methanol or methanol equivalents to halidepresent to produce an effective carbonylation ranges from about 1:1 to10,000:1, with the preferred range being from about 5:1 to about 1000:1.

[0043] In a preferred aspect of the invention, the vapor-phasecarbonylation method of the present invention may be used for makingacetic acid, methyl acetate or a mixture thereof The process includesthe steps of contacting a gaseous mixture comprising methanol and carbonmonoxide with a solid supported catalyst in a carbonylation zone andunder carbonylation conditions and recovering a gaseous product from thecarbonylation zone. The catalyst system includes a solid-phase componentcomprising platinum and tin deposited on an activated carbon support anda vaporous component comprising at least one of the halide promotersdescribed above.

[0044] The carbon monoxide may be fed to the carbonylation zone eitheras purified carbon monoxide or as a mixture of hydrogen and carbonmonoxide. Although hydrogen is not part of the reaction stoichiometry,hydrogen may be useful in maintaining optimal catalyst activity. Thepreferred ratio of carbon monoxide to hydrogen generally ranges fromabout 99:1 to about 2:1, but ranges with even higher hydrogen levels maybe useful.

[0045] The present invention is illustrated in greater detail by thespecific examples present below. It is to be understood that theseexamples are illustrative embodiments and are not intended to belimiting of the invention, but rather are to be construed broadly withinthe scope and content of the appended claims.

EXAMPLES Catalyst 1

[0046] In preparation the catalyst, 579 mg of dihydrogenhexachloroplatinate having an assay of 39.23 % (1.17 mmol of Pt) wasdissolved in 30 mL of distilled water. This solution was added to 20.0grams of 12×40 mesh activated carbon granules contained in anevaporating dish. The activated carbon granules had a BET surface areain excess of 800 m²/g. This mixture was heated using a steam bath andcontinuously stirred until the support granules became free flowing. Theimpregnated catalyst was then transferred to a quartz tube measuring 106cm long by 25 mm outer diameter. The quartz tube was thereafter placedin a three-element electric tube furnace so that the mixture was locatedin the approximate center of the 61 cm long heated zone of the furnace.Nitrogen was continuously passed through the catalyst bed at a rate of100 standard cubic centimeters per minute. The tube was heated fromambient temperature to 300° C. over a 2 hour period, held at 300° C. for2 hours and then allowed to cool back to ambient temperature.

[0047] To the catalyst prepared above was added a solution having 0.263grams (1.17 mmol) of tin (II) chloride dihydrate dissolved in a mixtureof 10 mL of 11.6 M HCl and 20 mL of distilled water. The catalystmixture was heated again using the steam bath and continuously stirringuntil the granules became free flowing. The impregnated catalyst wasthen transferred to a quartz tube measuring 106 cm long by 25 mm outerdiameter. The quartz tube containing the mixture was placed in athree-element electric tube furnace so that the mixture was located inthe approximate center of the 61 cm long heated zone of the furnace.Nitrogen was continuously passed through the catalyst bed at a rate of100 standard cubic centimeters per minute. The tube was heated fromambient temperature to 300° C. over a 2 hour period, held at 300° C. for2 hours and then allowed to cool back to ambient temperature.

[0048] The solid supported catalyst in accordance with the presentinvention, (Catalyst I) contained 1.09% Pt, 0.66% Sn, and had a densityof 0.57 g per mL.

Comparative Catalyst Example I

[0049] In preparing a comparative catalyst containing only platinum asthe active metal, 569 mg of dihydrogen hexachloroplatinate having a Ptassay of 40%, (1.17 mmol of Pt) was dissolved in 30 mL of distilledwater. This solution was added to 20.0 g of 12×40 mesh activated carbongranules contained in an evaporating dish. The activated carbon granuleshad a BET surface area in excess of 800 m²/g. This mixture was heatedusing a steam bath and continuously stirred until the support granulesbecame free flowing. The impregnated catalyst was then transferred to aquartz tube measuring 106 cm long by 25 mm outer diameter. The quartztube was thereafter placed in a three-element electric tube furnace sothat the mixture was located in the approximate center of the 61 cm longheated zone of the furnace. Nitrogen was continuously passed through thecatalyst bed at a rate of 100 standard cubic centimeters per minute. Thetube was heated from ambient temperature to 300° C. over a 2 hourperiod, held at 300° C. for 2 hours and then allowed to cool back toambient temperature.

[0050] The catalyst (Comparative Catalyst C-I) contained 1.10% Pt andhad a density of 0.57 g per mL.

Comparative Catalyst Example II

[0051] A second comparative catalyst was prepared by dissolving 0.29grams of nickelous acetate tetrahydrate (1.17 mmol) and 0.263 grams(1.17 mmol) of tin (II) chloride dihydrate in a solution consisting of20 mL of distilled water and 10 mL of 11.6 M HCl. The solution was thenadded to 20.0 g of 12×40 mesh activated carbon granules contained in anevaporating dish. The activated carbon granules had a BET surface areain excess of 800 m²/g. The impregnated catalyst was then transferred toa quartz tube measuring 106 cm long by 25 mm outer diameter. The quartztube was thereafter placed in a three-element electric tube furnace sothat the mixture was located in the approximate center of the 61 cm longheated zone of the furnace. Nitrogen was continuously passed through thecatalyst bed at a rate of 100 standard cubic centimeters per minute. Thetube was heated from ambient temperature to 300° C. over a 2 hourperiod, held at 300° C. for 2 hours and then allowed to cool back toambient temperature.

[0052] The catalyst (Comparative Catalyst C-II) contained 0.33% Ni,0.67% Sn, and had a density of 0.57 g per mL.

Comparative Catalyst Example III

[0053] A third comparative catalyst was prepared by dissolving 0.207grams (1.17 mmol) of palladium chloride in 10 mL of 11.6 M HCl. In aseparate vessel, 0.263 grams of tin (II) chloride dihydrate weredissolved in 10 mL of 11.6 M HCl. Both solutions were combined and mixeduntil uniform and the solution of dissolved palladium and tin wasdiluted with 10 mL of distilled water. The solution was then added to20.0 g of 12×40 mesh activated carbon granules contained in anevaporating dish. The activated carbon granules had a BET surface areain excess of 800 m²/g. The impregnated activated carbon granules werethen dried using the procedure described above.

[0054] The catalyst (Comparative Catalyst C-III) contained 0.61 % Pd,0.68% Sn, and had a density of 0.57 g per mL.

Comparative Catalyst Example IV

[0055] A fourth comparative catalyst was prepared using the proceduredescribed above to prepare the platinum catalyst in Comparative CatalystExample I, except 418 mg (1.17 mmol) of iridium trichloride hydrate wereused in place of the dihydrogen hexachloroplatinate. The catalyst(Comparative Catalyst C-IV) contained 1.10 % Ir.

Carbonylation of Methanol

[0056] The reactor system consisted of a 800 to 950 mm (31.5 and 37inch) section of 6.35 mm (¼ inch) diameter tubing constructed ofHastelloy C alloy. The upper portion of the tube constituted the preheatand reaction (carbonylation) zones. These zones were assembled byinserting a quartz wool pad 410 mm from the top of the reactor to act assupport for the catalyst, followed sequentially by: (1) a 0.7 g bed offine quartz chips (840 microns); (2) 0.5 g of one of the catalystsprepared as described in the preceding examples; and (3) an additional 6g of fine quartz chips. The top of the tube was attached to an inletmanifold for introducing liquid and gaseous feeds.

[0057] The six grams of fine quartz chips acted as a heat exchangesurface to vaporize the liquid feeds. Care was taken not to allow any ofthe liquid feeds to contact the catalyst bed at any time, includingassembly, start-up, operation, and shutdown. The remaining lower lengthof tubing (product recovery section) consisted of a vortex cooler whichvaried in length depending on the original length of tubing employed andwas maintained at approximately 0-5° C. during operation.

[0058] The gases were fed using Brooks flow controllers and liquids werefed using a high performance liquid chromatography pump. The gaseousproducts leaving the reaction zone were condensed using a vortex cooleroperating at 0-5° C. The product reservoir was a tank placed downstreamfrom the reactor system. The pressure was maintained using a modifiedResearch control valve on the outlet side of the reactor system and thetemperature of the reaction section was maintained using heating tape onthe outside of the reaction system.

[0059] Feeding of hydrogen and carbon monoxide to the reactor wascommenced while maintaining the reactor at a temperature of 240° C. anda pressure of 17.2 bara (250 psia). The flow rate of hydrogen was set at25 standard cc/min and the carbon monoxide flow rate was set at 100cc/min. The reactor section was maintained under these conditions for 1hour or until the temperature and pressure had stabilized, whichever waslonger. The high pressure liquid chromatography pump was then started,feeding a mixture consisting of 70 weight percent methanol and 30 weightpercent methyl iodide at a rate of 10-12 g per hour. Samples of theliquid product were collected and analyzed periodically using gaschromatographic techniques.

Carbonylation Example 1

[0060] The composition and weight of the samples taken periodicallyduring the procedure described above in which Catalyst I was used areset forth in Table I. “Time” is the total time of carbonylation (inhours) commencing with the feeding of the methanol until a particularsample was taken. In the tables “Mel” is the weight percentage of methyliodide present in the sample, “MeOAc” is the weight percentage of methylacetate present in the sample, “MeOH” is the weight percentage ofmethanol present is the sample and “HOAc” is the weight percentage ofacetic acid present in the sample. The weight of each sample is given ingrams. TABLE I Sample Expired MeOH Sample Number Time (h) MeI MeOAc (Wt.%) HOAc Weight (g) 1 3.00 15.01 6.25 72.06 0.1 45.9 2 5.00 14.83 6.1270.43 0.1 29.6 3 10.50 16.55 16.31 58.29 0.46 72.1 4 12.50 17.12 16.9560.78 0.48 28.9 5 18.00 16.64 16.5 58.98 0.48 81.5 6 20.00 13.62 39.2815.47 15.76 28.7 7 22.00 13.42 39.7 15.82 16.19 29 8 24.00 13.57 39.6315.78 16.12 28.5 9 26.00 15.1 39.23 18.91 12.06 28.9 10 29.00 15.2140.19 18.53 11.4 29.1 11 34.00 16 38.72 13.03 17.44 80.1 12 36.50 15.8639.26 13.24 17.7 24.1 13 42.00 15.98 38.47 13.06 17.56 81.5 14 44.0015.59 39.49 10.26 20.55 24.8 15 46.00 15.69 39.51 10.27 20.55 24.5

[0061] The rate of acetyl production based on the preceding experimentutilizing Catalyst I is set forth in Table II wherein Sample Number andTime values correspond to those of Table I, “Acetyl Produced” is theamount (millimoles) of methyl acetate and acetic acid produced duringeach increment of Time calculated from the formula:

(Sample Weight)×10×((weight % of MeOAc)/74)+((weight % of AcOH)/60)

[0062] “Production Rate” is the moles of Acetyl Produced per liter ofcatalyst volume per hour during each increment of Time (Time Increment),i.e., the time of operation between samples. The formula for determiningmoles of Acetyl Produced per liter of catalyst volume per hour is:

((Acetyl Produced)/(0.5×Time Increment))×0.57

[0063] wherein 0.5 is the grams of catalyst used and 0.57 is the densityof the catalyst in g/mL. TABLE II Acetyl Sample Number Expired Time (h)Produced (mmol) Rate (mol/L-h)  1 3.00 39.5 15.0  2 5.00 25.0 14.2  310.50 164.4 34.1  4 12.50 68.5 39.0  5 18.00 188.2 39.0  6 20.00 227.7129.8  7 22.00 233.8 133.3  8 24.00 229.2 130.6  9 26.00 211.3 120.4 1029.00 213.3 81.1 11 34.00 651.9 148.6 12 36.50 199.0 90.7 13 42.00 662.2137.3 14 44.00 217.3 123.9 15 46.00 214.7 122.4

[0064] Over the 46 hours of testing, the catalyst produced 3.55 moles ofacetyl. This represents a rate of 154 moles of acetyl/kg_(cat)-h or,represented as an hourly space velocity, 88 mol of acetyl/L_(cat)-h.

Comparative Carbonylation Examples

[0065] Comparative Catalysts C-I-C-IV, were utilized in thecarbonylation of methanol according to the above-described procedure.The Production Rate, expressed in terms of moles of Acetyl Produced perkilogram of catalyst per hour and moles per liter of catalyst volume perhour, for each of Catalyst I and Comparative Catalysts C-I-C-IV, areshown in Table III. As can be seen from Table III, the catalyst inaccordance with the present invention is significantly more active thana catalyst using Pt as the sole active metal. Further, when compared totin promoted catalysts for the other members of the triad, platinum isfar superior to either nickel or palladium. Comparative Example C-4shows that carbonylation rates using the catalyst of the presentinvention are superior to those obtained using iridium alone on anactivated carbon support. TABLE III Carbonylation Production RateExample Catalyst in moles/kg_(cat)-h in moles/L_(cat)-h 1 I 154 88(Pt—Sn) C-1 C-1 89 45 (Pt) C-2 C-II 6 3 (Ni—Sn) C-3 C-III 19 11 (Pd—Sn)C-4 C-IV 93 53 (Ir)

[0066] Having described the invention in detail, those skilled in theart will appreciate that modifications may be made to the variousaspects of the invention without departing from the scope and spirit ofthe invention disclosed and described herein. It is, therefore, notintended that the scope of the invention be limited to the specificembodiments illustrated and described but rather it is intended that thescope of the present invention be determined by the appended claims andtheir equivalents. Moreover, all patents, patent applications,publications, and literature references presented herein areincorporated by reference in their entirety for any disclosure pertinentto the practice of this invention.

We claim:
 1. A vapor-phase carbonylation method for producing esters andcarboxylic acids from reactants comprising lower alkyl alcohols, loweralkyl alcohol generating compositions, and mixtures thereof, said methodcomprising contacting the reactants and carbon monoxide with a catalystin a carbonylation zone of a carbonylation reactor under vapor-phaseconditions and wherein said catalyst includes a catalytically effectiveamount of platinum and tin associated with a solid carrier material. 2.The method of claim 1 wherein said reactants are selected from the groupconsisting of lower alkyl alcohols having from 1 to 10 carbon atoms,alkane polyols having 2 to 6 carbon atoms, alkyl alkylene polyethershaving 3 to 20 carbon atoms and alkoxyalkanols having from 3 to 10carbon atoms and mixtures thereof.
 3. The method of claim 1 wherein saidreactant is methanol.
 4. The method of claim 1 wherein said reactant isdimethyl ether.
 5. The method of claim 1 wherein esters and carboxylicacids produced from said vapor phase include acetic acid, methyl acetateand mixtures thereof.
 6. The method of claim 1 further comprisingcontacting said reactants in said carbonylation zone with a vaporoushalide compound selected from the group consisting of hydrogen iodide,hydriodic acid; methyl iodide, ethyl iodide, 1-iodopropane,2-iodobutane, 1-iodobutane, benzyl iodide, hydrogen bromide, methylbromide and mixtures thereof.
 7. The method of claim 6 wherein saidhalide is selected from the group consisting of iodine, hydrogen iodide,methyl iodide, bromine, hydrogen bromide, methyl bromide and mixturesthereof.
 8. The method of claim 1 wherein said carbonylation zone ismaintained at a temperature of about 100° C. to 350° C. and a pressureof about 1 to 50 bar absolute.
 9. The method of claim 1 wherein saidsolid carrier material is activated carbon.
 10. The method of claim 1wherein includes from about 0.1 weight percent to about 10 weightpercent each of said platinum and tin.
 11. The method of claim 1 whereinsaid catalyst includes from about 0.1 weight percent to about 2 weightpercent each of said platinum and tin.
 12. A vapor-phase carbonylationmethod for producing acetic acid, methyl acetate or a mixture thereofcomprising the steps of: a. under vapor-phase carbonylation conditionsof temperature and pressure, contacting a gaseous mixture comprisingmethanol, carbon monoxide, and a halide with a solid catalyst in acarbonylation zone of a carbonylation reactor wherein said solidcatalyst comprises from about 0.01 to about 10 weight % of platinum andfrom about 0.01 to about 10 weight % tin associated with a solid carriermaterial and wherein the weight % of the platinum and tin are based onthe total weight of the catalyst; and b. recovering acetic acid, methylacetate or a mixture thereof from the gaseous product.
 13. The method ofclaim 12 wherein said halide is selected from the group consisting ofhydrogen iodide, hydriodic acid; methyl iodide, ethyl iodide,1-iodopropane, 2-iodobutane, 1-iodobutane, benzyl iodide, hydrogenbromide, methyl bromide and mixtures thereof.
 14. The method of claim 13wherein said halide is selected from the group consisting of iodine,hydrogen iodide, methyl iodide, bromine, hydrogen bromide, methylbromide and mixtures thereof.
 15. The method of claim 12 wherein saidcarbonylation zone is maintained at a temperature of about 100° C. to350° C. and a pressure of about 1 to 50 bar absolute.
 16. The method ofclaim 12 wherein said catalyst includes from about 0.1 weight percent toabout 2 weight percent each of said platinum and tin.
 17. A vapor-phasecarbonylation method for producing acetic acid, methyl acetate or amixture thereof comprising the steps of: a. under vapor-phasecarbonylation conditions of temperature and pressure, contacting agaseous mixture comprising methanol, carbon monoxide, and a halide witha solid catalyst in a carbonylation zone of a carbonylation reactorwherein said solid catalyst comprises from about 0.1 weight % to about 2weight % of platinum and from about 0.1 weight % to about 2 weight % tinassociated with a solid carrier material and wherein the weight % of theplatinum and tin are based on the total weight of the catalyst; and b.recovering acetic acid, methyl acetate or a mixture thereof from thegaseous product.
 18. The method of claim 17 wherein said halide isselected from the group consisting of hydrogen iodide, hydriodic acid;methyl iodide, ethyl iodide, 1-iodopropane, 2-iodobutane, 1-iodobutane,benzyl iodide, hydrogen bromide, methyl bromide and mixtures thereof.19. The method of claim 12 wherein said carbonylation zone is maintainedat a temperature of about 100° C. to 350° C. and a pressure of about 1to 50 bar absolute.